Patches are always welcome! Currently we only work on GitHub, so you can create pull requests.
To get started with Android/BRNmod, you'll need to get familiar with Repo and Version Control with Git.
To initialize your local repository using the CyanogenMod trees, use a command like this:
repo init -u git://github.com/BRNmod/android.git -b brn-12.1
Then to sync up:
repo sync
Please see the CyanogenMod Wiki for building instructions, by device.